Purification of phenol

ABSTRACT

PHENOL PRODUCED BY DECOMPOSITION OF CUMENE HYDROPEROXIDE IS PURIFIED BY HEATING WITH HYDROBROMIC OR HYDROIODIC ACID, OR THEIR WATER-SOLUBLE SALTS, FOLLOWED BY DISTILLATION. THIS TREATMENT NOT ONLY REDUCES CARBONYLBEARING IMPURITIES, BUT ALSO REDUCES METHYLBENZOFURAN IMPURITIES.

United States Patent 3,810,946 PURIFICATION OF PHENOL Chuen Y. Yeh, Snccasunna, and Harry E. Ulmer, Morristown, N.J., assignors to Allied Chemical Corporation, New York, N.Y. No Drawing. Filed Nov. 3, 1972, Ser. No. 303,558 Int. Cl. C07c 37/38 US. Cl. 260-621 A 12 Claims ABSTRACT OF THE DISCLOSURE Phenol produced by decomposition of cumene hydroperoxide is purified by heating it with hydrobromic or hydroiodic acid, or their water-soluble salts, followed by distillation. This treatment not only reduces carbonylbearing impurities, but also reduces methylbenzofuran impurities.

BACKGROUND OF THE INVENTION Production of phenol by oxidation of cumene and decomposition of the resulting hydroperoxide in the presence of acidic catalysts is well known. The decomposition product contains phenol and acetone as the principal products along with minor amounts of various side products. Fractional distillation of the decomposition product yields phenol of purity suflicient for many uses. Such phenol product, however, is unsatisfactory for certain purposes because it discolors on aging in that it becomes yellow or pink, and it discolors on chlorination or sulfonation.

Discoloration on sulfonation, and especially on chlorination, results from the presence of certain carbonylbearing impurities, especially ketonic impurities, as well as of methylbenzofurans, which are not separated by ordinary fractional distillation. These impurities are generally present in amounts exceeding 400 p.p.m. Ketonic impurities principally include mesityl oxide, acetol and acetophenone. Methylbenzofurans (both 2-methylbenzofuran and 3-methylbenzofuran) are generally present in amounts exceeding 100 p.p.m.

DISCUSSION OF THE PRIOR ART It is known to purify phenol obtained from the decomposition product of cumene hydroperoxide by treating it with an acid selected from the group consisting of inorganic and strong organic acids at elevated temperature, neutralizing the acidified phenol and distilling it.

It is also known to purify phenol obtained by decomposition of cumene hydroperoxide by treating it with bases, including amines, followed by neutralization and distillation.

Unfortunately, however, known purification methods for phenol obtained by decomposition of cumene hydroperoxide are often incapable of eliminating or substantially reducing methylbenzofuran impurities.

SUMMARY OF THE INVENTION In accordance with the present invention, pure phenol, substantially free from methylbenzofurans, is obtained from the decomposition product of cumene hydroperoxide comprising phenol and acetone from which products boiling lower than phenol have been removed by distillation by contacting it at a temperature of about 40 to 220 C. with 0.01 to 2.0 percent by Weight of a treating agent selected from the group consisting of hydrobromic acid, hydroiodie acid, their water-soluble salts and mixtures thereof and distilling it.

DETAILED DESCRIPTION OF THE INVENTION The phenol product which can advantageously be purified in accordance with the method of the present invention has been obtained by decomposition of cumene hydroperoxide to form phenol and acetone as principal products, followed by distillation to remove the products boiling lower than phenol, e.g., acetone. Preferably, the phenol product has also been subjected to further distillation to separate it from by-products having a boiling point higher than that of phenol.

The treating agents of the present invention interact with or bind carbonyl bearing impurities as well as methylbenzofurans in such manner that following treatment phenol free of these impurities can be recovered by distillation. The amount of treating agent required is, to some extent, dependent upon the concentration of the impurities present in the phenol. In general, the amount of treating agent used is about 0.01 to 2 percent, preferably about 0.03 to 1.0 percent of anhydrous treating agent, based on the weight of the phenol. It is to be understood, however, that the treating agent may be used in anhydrous form as well as in aqueous solutions of any desired concentration, but ordinarily in concentration of about 40 percent by weight of its aqueous solution.

The exact temperature at which the phenol is treated with the treating agent in accordance with the present invention is not critical. Generally, treatment is carried out at temperatures from 40 to 220 0, preferably 60 to 200 C. and more preferably yet at to C. The time of treatment should be sufficiently long to permit the desired reaction to take place. In general, reaction can be obtained in one minute, with a minimum of time of about five minutes being preferred. For optimum results, treating times of from 0.5 to 6 hours may be employed.

Ordinarily, it will be desirable to neutralize the treated phenol if hydrobromic or hydroiodic acid have been employed as treating agent, as is preferred practice, so as to avoid loss of phenol which may occur through side reactions in subsequent distillation and to avoid or reduce corrosion of equipment. Neutralization may conveniently be elfected by adding liquid or finely pulverized alkaline acting agents, such as alkali metal or alkaline earth metal, oxides, hydroxides, carbonates or bicarbonates, or their solutions. Ammonia, aqueous or anhydrous, as well as its alkaline-acting derivatives, such as amines, monoas well as polyamines, are also suitable as neutralizing agents. Alkali metal hydroxides and carbonates are preferred neutralizing agents. It will usually be preferred to employ the neutralizing agent'in about the stoichiometric proportions required to neutralize the acidic treating agent.

The distillation following treatment with treating agent in accordance with the present invention can be carried out at atmospheric pressure, reduced pressure or superatmospheric pressure in the absence or presence of small amounts of water, say not more than about 5 percent by weight or, more preferably, not more than about 2 percent by weight of water, based on the phenol. Preferably, it is carried out at atmospheric pressure or reduced pressure at temperatures of 80 to 0., depending upon the pressure in the system.

The following examples are given to further illustrate the invention, to describe preferred embodiments and to set forth the best mode presently contemplated by us of carrying out the invention. It is to be understood, however, that the invention is not to be limited by the details described therein.

Generally, in preferred operation crude phenol obtained by decomposition of cumene hydroperoxide from which higher and lower boiling decomposition products have been removed by distillation, is first treated with small amounts, i.e. 0.05 to 0.5 percent by weight of hydrobromic or hydroiodic acid or mixtures thereof, for a period of from one to six hours at 100 to 120 C., the acid treating agent is neutralized by addition of alkali metal hydroxide or carbonate, and the phenol is distilled to obtain the purified phenol as overhead product containing less than 100 p.p.m. total impurities and substantially no methylbenzofurans.

In the following examples, methylbenzofuran impurities are determined by gas chromatography using conventional procedures.

EXAMPLE 1 COMPARATIVE EXPERIMENT 1 The procedure of Example 1 is repeated using identical phenol but containing 162 p.p.m. of 3-methylbenzofuran and substituting 0.40 gram (0.2 percent) by weight of sulfuric acid for the hydrobromic acid. The results are summarized in Table 1 below.

COMPARATIVE EXPERIMENT 2 Example 1 is repeated using identical phenol but containing 153 p.p.m. of B-methylbenzofuran and substituting 0.40 gram (0.2 percent by weight) of hydrochloric acid for the hydrobromic acid. Results are summarized in Table I below.

TABLE I Treating agent H280 HCl, HBr, Comp. Comp. Ex. 1 Exp. 1 Exp. 2 Treating time (hours) 3-methylbenzo1uran (p.p.m.)

The data in Table I clearly demonstrate that under the conditions of the present invention, hydrobromic acid efi'ectively reduces S-methylbenzofuran content of phenol, whereas sulfuric acid and hydrochloric acid do not substantially reduce 3-methy1benzofuran.

EXAMPLE 2 A quantity of the same phenol starting material as used in Example 1 containing 151 p.p.m. of B-methylbenzo- .4 furan is treated with 0.2 percent by weight of hydrobromic acid at 115 C. for six hours, after which time 0.21 percent by weight of sodium hydroxide is added in form of a 50 percent aqueous solution. Final pH of the phenol is 7.0. The phenol so treated is then distilled under reduced pressure at a pot temperature of about C. using a reflux rate of about 4:1. Cuts are taken and analyzed for 3-methylbenzofuran content. The results are summarized below:

Percent by 8-methy1- weight benzoiurnn distilland (p.p.m.)

Cutlnumber:

COMPARATIVE EXPERIMENT 3 The procedure of Example 2 is repeated using the identical phenol starting material containing 162 p.p.m. of added 3-methylbenzofuran, but substituting sulfuric acid for the hydrobromic acid. Final pH of the treated neutralized phenol is 6.5. The mixture is distilled and cuts are taken and analyzed for 3 methylbenzofuran as in Example 2. Results are summarized below:

3-methylbenzoturan (op- 0 COMPARATIVE EXPERIMENT 4 Percent by 3-methylweight 0! benzofuran distillend (p.p.m.)

Cut number:

The above data demonstrate the effectiveness of hydrobromic acid in reducing 3-methylbenzofuran contamination of phenol, as compared to the ineffectiveness of sulfuric acid and hydrochloric acid for that purpose.

EXAMPLE 3 Phenol starting material containing 438 p.p.m. of 2 methylbenzofuran is treated with 0.20 percent by weight COMPARATIVE EXPERIMENT 5 The procedure of Example 3 is repeated using identical phenol, but containing 374 p.p.m. of Z-methylbenzofuran and substituting 0.20 percent by weight of sulfuric acid for the hydrobromic acid. The results are summarized in Table II below.

COMPARATIVE EXPERIMENT 6 The procedure of Example 3 is repeated using identical phenol, but containing 232 p.p.m. of Z-methylbenzofuran and substituting 0.20 percent by weight of hydrochloric acid for the hydrobromic acid. The results are summarized in Table II below.

TABLE II Treating agent H280 HCl, HBr, Comp. Comp. Ex. 3 Exp. 6 Exp. 6 Treating time (hours) Z-methylbenzoiuran (p.p.m.)

438 374 232 374 l 695 i 443 257 l 790 N.A. 183 l 890 I 476 66 1 440 I 498 57 I 430 i 536 55 358 i 550 New impurity formed, eluting at same retention time as Z-methylbenzofuran, which is converted to giflerent higher boiling compound(s) after hours of ea mg.

=New impurity formed, eluting at same retention time as 2-methylbenzoiurau.

EXAMPLE 4 Percent by 2-methylweight of benzoiuran distilland (p.p.m.)

COMPARATIVE EXPERIMENT 7 Example 4 is repeated using identical phenol containing 374 p.p.m. of added 2-methylbenzofuran, but substituting 0.20 percent by weight of sulfuric acid for the hydrobromic acid. Following neutralization the phenol so treated is distilled under reduced pressure of 32 to 36 mm. Hg at pot temperature of about 111 to 113 C. Cuts are taken and analyzed for 2-methylbenzofuran content. The results are summarized below:

Percent by 2-methylweight of benzoiuran distllland (p.p.m.)

Cut number:

3. 6 l, 600 4. U 970 9. 2 980 64. 2 130 5. 7 N.A. 6. 7 3B COMPARATIVE EXPERIMENT 8 Percient by 2-methylw ght o1 benzoiuran distilland (p.p.m.)

The above shows that treatment of phenol containing Z-methylbenzofuran with sulfuric or hydrochloric acid does not eifect reduction of Z-methylbenzofuran content, but indeed results in formation of other impurities eluting at the same place as Z-methylbenzofuran. Treatment of phenol contaminated with Z-methylbenzofuran with hydrobromic acid, as shown in Example 4, effectively reduces 2-methylbenzofuran contamination.

We have found that chlorination number of phenol is substantially aflfected by methylbenzofuran at both 490 and 540 mg. The Z-methylbenzofuran has an equal affect at both wavelengths, whereas 3-methylbenzlofuran afiects the chlorination number principally only at 490 III/1.. Chlorination number is determed by placing 10:0.1 grams of the phenol to be tested in a chlorination vessel fitted with a gas inlet tube extending to the bottom of the vessel. The bottom of the inlet tube is constructed of fritted glass to allow fine dispersion of chlorine as it enters the liquid phenol. The vessel is placed in an oil bath and the sample brought to C. Chlorine gas is introduced into the phenol at a rate of 4 liters per hour at a temperature of 80:3 C. until a weight gain of 5.5 to 6 grams is obtained. The sample is weighed periodically to confirm 55 to 60 percent chlorination. It is then transferred to a one centimeter cell for analysis by a recording spectophotometer. The absorption maxima at 490 and 540 m are noted for test purposes. If the absorbance is. too great for the one centimeter cell, a 0.1 cm. cell may be used, or ten-fold dilution of the sample with chloroform may be employed, and the recorded absorbance is multiplied by a factor of ten.

EXAMPLE 5 neutralization at 80 C. with 0.23 weight percent sodium hydroxide. The treated phenol is: distilled at 115 C. pot temperature and fractions are collected and analyzed for impurities usually present in commercial grade cumene at 115 C. pot temperature and fractions are collected and analyzed for the various impurities commonly found in commercial cumene phenol. Results are given in Table VI.

TABLE V Impurities Acetone MOI Cu Acetol AMS MB]? AP" DMPC Unk' Total Chlorination number atcharge Comments 490 my 540 mu phenol. Results are shown in Table V. The results demonstrate removal of methylbenzofurans as well as of other impurities present in commercial grade cumene phenol.

l Mflfiflfl$fi m m fi mm W .m m w m m mwwmmfimmfi We 1 h 1 m m .n h m T w a S C .1 6 .1 uh I mmmmmmww Mw m .wfi U m m flflwwwm ww u m m m 1 P U m u w m P m 000000 .000000000 0 w m 6 N m 0 00000000 0 .1 1 h v. r r Pm P n d M V e e H M hm n 0 D y m 0 mm 90690000 000000000 h d e 0 000 00 0 w 22 M W m m n m1 0 0 .l A m .m m h J M m M008000 m00000000O I W a m. W. OOO m0 D. 2 n e .m m w n B 0 S o r M m m m cf u. r w m e e m m OOOOOO "000000000 w m 4 00132100 8 o v .t p s 2 1 m n m w m m M 1. A k 6 e H a P m M 0 B 4 X t m e w v. e m m s 0 m V. A .1 220001 211004000 m M h m V m I l 5 30000012 0 z T r. a n V n 2 u m E C 0 k L 4 011000 000000000 WW B s 00001000 0 1 u m w m m m m 9 I I M om I ma mm m Am 1 9 u u 0 mm m t 5 n fl\ W. n H n m n n 9 u n u n a m w n n n n n u u we yi 1 m n n n n n hm bd 0 mm H u n 2 7 .1 if m m 31 mmmu m z m 1 0 u e h h 4 .0 h n n km .md P on n n n u u n n we. 6 a e n n f. W 1 9 A .O. A E b a 0 8 0 0m 0 4. 8 6 n %n n W" .2... ti L H m 1 5 2 dd 0 P 1 O r C u .61... n O 1 8 5 .200 S M n e 8 u "m" w w um e w p. a n 1 m n 9. M dm m m ata heaena E u u t n m hm Dim .We 1 233326m401 m m m .t nm J E e 0 g e n an. ..ooa1oc d w 0 F. H. .NC ma e h c 0 r p m I o n u 1 tLewmeetaaaaaLae ta m 5 n u n u u 0 YR L h 0 a 0 6 .10 l n 1 m c mu m m m m I t m a 1 6 r. m e w amf b S 6 g AMn ue lm ....0 t w 12W A C W m n 1234567891 u 0 :1 u 0 L .m o m m 9 0 nol alpha-methyl styrene dimers, and the like were not analyzed and are not included in total impurities."

Alpha-methylstyrene. Methyl benzoiurnas. 'Acetophenone. T Dimethyl phenyl carbinol. l Un- EXAMPLE 7 A sample of commercial phenol containing 118 p.p.m. 75 methyl benzofurans with 614 p.p.m. total impurities is heated with 0.01 weight percent of hydrobromic acid at h boilers such as curnyl phe I Cumene.

11 Residue. Loss.

1 Mesityl oxide. known.

all impurities boiling higher than phenol, is treated with 0.2 weight percent hydrobromic acid at 115 C. for three hours and is then neutralized at 80 C. with 0.23 weight percent sodium hydroxide. The treated mixture is distilled 9 115 C. for four hours, followed by distillation. No methyl tions can be affected without departing from the scope benzofurans were found in the mid-70 percent cut colof the novel concepts of the present invention, and the lected during distillation. Total impurities of starting illustrative details disclosed are not to be construed as phenol and purified phenol are shown below. This example imposing undue limitations on the invention. illustrates efiiciency of hydrobromic acid in removing im- We claim: purities, including methyl benzofurans, when used in 5 1. A process for the purification of phenol obtained amount of 0.1 percent by weight. from the decomposition product of cumene hydroper Impurities (p.p.m.)

Optical density at- T t l 490 m 540 m l Acetone MO Cu 1 Acetol AMS MBF AP DMPC Unk T p.p.m.

Starting phenol 11. 5. 50 6 259 9 212 3 118 0 0 7 614 Purifie phenol 0. 78 0.38 6 0 2 0 0 D 0 0 33 41 k Mesityl oxide. Cumene. Alpha methylstyrene. Methyl benzolurans. Aeetophenone. 'Dimethyl phenyl carbinol. 1 Unnown.

EXAMPLE 8 oxide, from which products boiling lower than phenol 0 have been removed by distillation, which comprises contacting the phenol at a temperature of 40 to 220 C. with 0.01 to 2.0 percent by weight of a treating agent se- A portion of the same phenol as used in Example 7 is 2 heated with 0.1 percent by weight hydroiodic acid at 990 C. for six hours, followed by neutralization with 0.03 per- 1 d f th f h d b cent sodium hydroxide distillation. A 70 percent heart out ecte i e F cn s1stmg o y w is collected, a portion of which is analyzed for impurities, and hydrolodc acid and mlxtures thereof and dlstlumg while another portion is chlorinated in accordance with 25 the Phenolabove-described procedure. This example illustrates the The Process of claim 1 wherein the Phenol is 0011 efiicacy of hydrobromic acid for removal of impurities, tacted With the treating agent at a tempcl'atul'e 0f including methyl benzofurans, from phenol containing 200 C. and wherein the treating agent is employed in them for purification. amount of 0.03 to 1.0 percent by weight.

Impurities (p.p.m.)

Optical density at- T t I o a 490 mp 540 mp Acetone MO 1 Cu 1 Acetol AMS MBF AP DMPC Unk 1 p.p.m

Starting phenol 11.50 5.50 6 259 9 212 3 118 0 0 7 614 Purified phenol 1.14 4 0 5 0 5 5 0 0 45 62 Mesityl oxide. Cumene. 'Alpha-methylstyrene. Methyl benzolurans. Acetophenone. 'Dimethyl phenyl carbinol. Unknown.

EXAMPLE 9 3. The process of claim 2 wherein the phenol is contacted with the treating agent for a period of 0.5 to 6 hours.

4. The process of claim 3 wherein the phenol, prior to 45 contacting it with the treating agent, has been distilled to separate it from products boiling higher than phenol.

5. The process of claim 1 wherein the treating agent A portion of the same phenol as used in Example 6 is heated with 0.20 percent by weight of sodium bromide at 115 C. for two hours, followed by distillation. A percent heart out is collected, a portion of which is analyzed for impurities, while another portion is chlorinated in accordance with above-described procedure. This example illustrates efficacy of sodium bromide for removal of is hydrobromic acidmethylbenzofuran impurities from phenol containing the F0 The P f clalm 5 h Phenol, P same. 0 to contacting it with the hydrobromic acid, has been dis.-

Impurities (p.p.m.)

Optical density at- Total 490 inp 740 m Acetone MO 1 Cu Acetol AMS 1 MBF 4 AP DMPC Unk 1 p.p.m.

Startin henoL- 47. 5 32. 5 118 92 25 93 1, 223 202 24. 495 0 59 26, 309 Purifiec i ghenoln 5. 3. 05 3 95 1 0 10 24 0 0 51 190 Mesityl oxide. cumene. Aipha-methylstyrene. Methyl benzoiurans. Acetophenone. 'Dimethyl phenyl carbinol. Unknown.

When in the above examples hydroiodic acid is subtilled to separate it from products boiling higher than stituted for the hydrobromic acid, similar results are obph n ltained, that is to say, contamination of phenol obtained 65 P of 6 the Phenol 1S n from decomposition f cumene hydropemxide with tacted with the hydrobromic acid for a period of 0.5 to 6 meth lbenzofuran and 3-meth ibenzofuran is elfectivel hours at a tempeliamre of 600 F9 and i reducyed on the other hand, g phenol Obtained by the phenol following contact with the hydrobromic acid composition of cumene hydroperoxide containing methYL but before distillation 1s neutralized by adding an alkaline acting agent. benzofurans is treated with other morganlc or strong 70 The process of claim 6 wherein the Phenol is com organic acids, such as phosphoric acid, toluene sulfonic meted for a period of 05 to hows at a temperature of acid, benzosultonic acid or chlorinated sulfonic acids, to with 005 to {L5 percent by weight of then a Corresponding decrease in methylhehlofurahs is hydrobromic acid, followed by neutralization by adding a not obtained. 75 neutralizing agent selected from the group consisting of It will be apparent that many modifications and variaalkali metal hydroxides and carbonates.

9. The process of claim 1 wherein the treating agent is hydroiodic acid.

10. The process of claim 9 wherein the phenol is contacted with 0.03 to 1 percent by weight of hydroiodic acid at a temperature of 60 to 200 C.

11. The process of claim 10 wherein the phenol has been distilled prior to contacting it with hydroiodic acid to separate it from products boiling lower than phenol.

12. The process of claim 11 wherein the phenol is treated with the hydrobromic acid for 0.5 to 6 hours, followed by neutralization by adding neutralizing agent selected from the group consisting of alkali metal hydroxides and carbonates.

References Cited UNITED STATES PATENTS LEON ZITVER, Primary Examiner N. MORGENSTERN, Assistant Examiner US. Cl. X.R. 

